JPH0361087A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To enable an image of satisfactory density to be formed using low printing energy without any storage or fusion problem and also a high density and definition image to be formed using the same amount of printing energy by allowing a sensitizer and a specific polymer mold release agent to be present in a dye layer. CONSTITUTION:A dye layer consisting of dye, binder, sensitizer and mold release agent is provided on a base film. The sensitizer is a low molecular weight material with a melting point of 50 to 150 deg.C and is a graft copolymer having at least, one kind of mold release segment selected from among polycyclohexane segment, carbon fluoride segment and long-chain alkyl segment, to which main chain the mold lubricant is graft-bonded. The recommended sensitizers are thermally plastic resin oligomer, aromatic compound and various types of wax.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a thermal transfer sheet, and more specifically, it is useful for a thermal transfer method using sublimable dyes (thermally transferable dyes), and is useful for improving storage stability and dye retention during thermal transfer. The purpose of the present invention is to provide a thermal transfer sheet that has excellent transfer properties and can provide excellent image density.

(Prior art) Inkjet methods, thermal transfer methods, etc. have been developed as methods for providing excellent monochrome or full-color images easily and at high speed in place of conventional general printing methods. The most excellent method is the so-called sublimation thermal transfer method, which uses sublimable dyes, as it has excellent continuous gradation properties and provides full-color images comparable to color photographs.

The thermal transfer sheet used in the above-mentioned sublimation type thermal transfer method has a dye layer consisting of a sublimable dye and a binder formed on one side of a base film such as a polyester film, and
In order to prevent the thermal head from sticking, a base film with a heat-resistant layer provided on the other side is generally used.

The dye layer surface of such a thermal transfer sheet is placed on a transfer material having an image-receiving layer made of polyester resin, etc., and the dye in the dye layer is transferred to the transfer material by heating it in an imagewise manner from the back side of the thermal transfer sheet with a thermal head. The desired image is formed.

(Problems to be Solved by the Invention) In the thermal transfer method as described above, only the dye in the dye layer is transferred to the transferred material, and the binder remains on the base film side. On this occasion,
The better the transferability of the dye, the clearer and higher density the image will be formed.

The easiest way to improve dye migration is to increase printing energy, but high printing energy is undesirable as it increases printing costs, and it is also undesirable to use plastic as a base film. When using a film, there is a limit to the printing energy itself.

Another method is known to add low melting point compounds such as wax to the dye layer as a sensitizer, but when these low melting point compounds are added, the rolled thermal transfer sheet may become blocked. In addition, during thermal transfer, the dye layer fuses to the surface of the transfer material, making it difficult to remove.
When peeled off, a problem arises in that the dye layer peels off and transfers to the transfer material.

One possible way to solve these problems is to add fine particles such as silica to the dye layer as a release agent.
In this case, there is a problem that the transferred image becomes rough and the color reproducibility and resolution deteriorate. Additionally, there is a method of adding silicone oil as a mold release agent, but this silicone oil is not compatible with the dye layer, causing surface stickiness, discoloration of transferred images, and adversely affecting storage stability. There is a problem that the amount decreases.

Therefore, an object of the present invention is to be able to form an image of satisfactory density with lower printing energy compared to the conventional technology, without causing problems in storage stability or fusion, and to be able to form an image with a satisfactory density with lower printing energy than the conventional technology, and with the same printing energy as the conventional technology, it is possible to form an image with a satisfactory density. An object of the present invention is to provide a thermal transfer sheet capable of forming high-density and fine images.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides dyes, binders,
In a thermal transfer sheet provided with a dye layer consisting of a sensitizer and a release agent, the sensitizer is a low molecular weight substance with a melting point of 50 to 150°C, and the release agent is a polysiloxane graft-bonded to the main chain. This thermal transfer sheet is characterized in that it is a graft copolymer having at least one type of releasable segment selected from segment, fluorocarbon segment, and long-chain alkyl segment.

(For I) By having a sensitizer and a specific polymer release agent in the dye layer, printing energy can be satisfied with lower printing energy compared to conventional technology without causing storage stability or fusion problems. A thermal transfer sheet is provided that can form a high-density image, and can also form an even higher-density and finer image with the same printing energy as conventional ones.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The thermal transfer sheet of the present invention is basically formed by forming a dye layer on a base film in the same manner as in the prior art, but the dye layer is coated with a sensitizer and a specific release polymer. It is characterized by its inclusion.

The base film of the thermal transfer sheet of the present invention as described above may be any conventionally known film as long as it has a certain degree of heat resistance and strength, for example, 0.5 to 50.
μn], preferably paper with a thickness of about 3 to 1071 m,
Examples include various processed papers, polyester films, polystyrene films, polypropylene films, polysulfone films, aramid films, polycarbonate films, polyvinyl alcohol films, cellophane, etc., and polyester films are particularly preferred. These base films may be sheet-fed or continuous films, and are not particularly limited. Particularly preferred among these is a polyethylene terephthalate film whose surface has been previously treated to make it more adhesive.

The dye layer formed on the surface of the profiteering film is a layer in which at least a dye, a sensitizer, and a mold release agent are supported by an arbitrary binder resin.

The dye to be used is not particularly limited, as any dye used in conventionally known thermal transfer sheets can be effectively used in the present invention. For example, some preferred dyes include MS Red G, Mac
rolex Red Violet R, CeresR
ed7B, SamaronRedHBSL, Re5o1
inRedF3BS, etc., and yellow dyes include Holon Brilliant Yellow 6GL, PTY-
52, Macrolex Yellow 6G, etc., and
Blue dyes include Kaya Set Blue 14, Waxolin Blue AP-FW, and Holon Brilliant Blue S-.
Examples include R, MS Blue 100, and the like.

As the binder resin for supporting the above dye, any conventionally known binder resin can be used, and preferred examples include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate,
Examples include cellulose resins such as cellulose acetate butyrate, vinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acecool, polyvinyl pyrrolidone, polyacrylamide, and polyester. Among these, cellulose resins, acetal From the viewpoint of heat resistance, dye migration properties, etc., polyester-based dyes, butyral-based dyes, butyral-based dyes, and polyester-based dyes are preferred. In addition, these binders preferably have a Tg of 50°C or higher; if the Tg is lower than 50°C, the binder tends to soften when the sensitizer melts during thermal transfer, and the dye layer tends to fuse to the transfer material. This is not desirable.

The sensitizer used in the present invention is 50 to 150"C
If the melting point is less than 50°C, the sensitizer will easily migrate to the dye surface, causing problems such as blocking. On the other hand, if the melting point exceeds 50°C, the sensitizer will migrate to the dye surface, causing problems such as blocking. This is not preferred because the sensitization effect decreases rapidly.

Further, the sensitizer used in the present invention has a molecular weight of 100 to 1,
A range of 500 is preferable; if the molecular weight is less than 100, it will be difficult to maintain the melting point above 50°C; on the other hand, if the molecular weight exceeds 1,500, the sharpness of the sensitizer melting during thermal transfer will be lost, resulting in This is not preferred because the sensitization effect will be insufficient.

Further, the sensitizer is a binder 100 forming a dye layer.
It is preferably used in a ratio of 1 to 100 parts by weight; if the amount used is less than 1 part by weight, it is difficult to obtain a satisfactory sensitizing effect, while if it exceeds 100 parts by weight, the heat resistance of the dye layer will decrease. So I don't like it.

The sensitizer described above may be any known low molecular weight substance as long as it has a melting point of 50 to 150'C, but preferred sensitizers in the present invention include thermoplastic resin oligomers, such as polyurethane oligomers, Polystyrene oligomer, polyester oligomer, polyacrylic oligomer, polyethylene oligomer, polyvinyl chloride oligomer, polyvinyl acetate oligomer, ethylene/vinyl acetate copolymer oligomer, ethylene acrylic copolymer oligomer, polyoxyethylene oligomer, polyoxypropylene oligomer, Various oligomers such as polyoxyethylene propylene oligomer; fatty acids such as myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, and montanic acid, caproic acid amide, caprylic acid amide, lauric acid amide, stearic acid amide, oleic acid amide , fatty acid amide such as eicosenoic acid amide, methyl behenate, methyl lignocerate, methyl montanate, pentadecyl palmidate,
Hexacosyl stearate, carbamic acid [1,4 phenylene bis(methylene)] bis dimethyl ester, fatty acid esters, etc., 1,4-dicyclohexylbenzene, benzoic acid, aminobenzophenone, dimethyl terephthalate, fluoranthene, phenols, naphthalenes. , aromatic compounds such as phenoxy compounds, and various waxes.

The mold release agent used in the present invention is a polymer having at least one type of mold release segment, and the mold release segment is graft-bonded as a side chain to the main chain of the polymer.

The releasable segments of such polymers are themselves numerically less compatible with the main chain of the polymer. Therefore, when such a polymer is added to a dye layer or when a dye layer is formed using this release polymer as a binder, the release segments tend to undergo microphase separation from the dye layer and bleed onto the surface of the dye layer. . On the other hand, the main chain is integrated with the dye layer and adhered to the base film. As a result of these effects, the surface of the dye layer becomes rich in releasable segments and exhibits good releasability. However, the releasable segment does not separate from the dye layer due to the main chain, so the releasable segment does not migrate to the surface of another article such as a transfer material.

The releasable polymer is a graft copolymer having at least one releasable segment selected from a polysiloxane segment, a fluorocarbon segment, and a long-chain alkyl segment graft-bonded to the main chain.

As the polymer for the main chain, any conventionally known polymer having a reactive functional group can be used, and preferred examples include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and vinegar. Cellulose resins such as cellulose butyrate, acrylic resins, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acecool, bobbinylpyrrolidone, vinyl resins such as polyacrylamide, polyamide resins, polyurethane resins, polyester resins, etc. Among these, acrylic, vinyl, polyester, polyurethane, polyamide or cellulose resins are particularly preferred from the viewpoint of compatibility with the binder.

The above-mentioned releasable copolymer can be synthesized by various methods, and one preferred method is to synthesize the releasable copolymer by, after forming the main chain,
A method may be mentioned in which a functional group present in the main chain is reacted with a releasable compound having a functional group that reacts with the functional group.

One example of the mold release compound having the above functional group is: Examples include the following compounds.

(a) Polysiloxane compound In the above formula, some of the methyl groups may be substituted with other alkyl groups or aromatic groups such as phenyl groups.

(b) Carbon fluoride compound (8) (:, F, 7(1:2H40H(9) C
6F, 3C2H40H (11) (12) (13) (14) (15) (16) (17) C8F, □C2H40H C,, F2. C2H40H C8F+73O□N (C2H5) C2H40HC, Fl
? 5O2N(C2H8)C2H40H(:,F,3CO
OH C6F,, GOCI CBF, 7C2H4SH (18) HaC, oF2. C2H, 0CH2CH-CH2 (c) Long chain alkyl compounds Higher fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid and their acid halides, nonyl alcohol, caprylic alcohol, lauryl alcohol, myristyl Alcohol, higher alcohols such as cetyl alcohol, stearyl alcohol, oleyl alcohol, lysyl alcohol, lysyl alcohol, higher aldehydes such as capric aldehyde, lauric aldehyde, myristic aldehyde, stearic aldehyde, higher amines such as decylamine, lauryl amine, cetyl amine, etc. .

The above examples are merely illustrative, and various other reactive mold-releasing compounds are available from Shin-Etsu Chemical, etc., and any of them can be used in the present invention. Particularly preferred is a monofunctional release compound having one functional group in one molecule, and when a polyfunctional compound having two or more functionalities is used, the graft copolymer obtained is unfavorable because it tends to gel.

The relationship between the functional mold-releasing compound and the main chain polymer as exemplified above is as shown in Table 1 below, where the functional group of the mold-releasing compound is represented by X and the functional group of the main chain polymer is represented by Y. becomes. Of course, the relationship between X and Y may be reversed, or they may be used in combination, and the invention is not limited to these examples as long as they react.

Another preferred manufacturing method is to react the functional mold-releasing compound with a vinyl compound having a functional group that reacts with the functional mold-releasing compound to obtain a monomer having a mold-releasing segment. A desired graft copolymer can be similarly obtained by copolymerizing with.

Still another preferable production method is to add the exemplified compound (7) to a polymer having an unsaturated double bond in its main chain, such as an unsaturated polyester or a copolymer of a vinyl monomer and a diene compound such as butadiene. Examples include a method of grafting by adding a mercapto compound such as ) or the above-mentioned releasable vinyl compound.

The above are examples of preferred production methods, and the present invention can of course also use graft copolymers produced by other methods.

The content of the releasable segment in the above polymer is such that the amount of the releasable segment is 3 to 60% by weight in the polymer.
If the amount of the releasable segment is too small, the releasability will be insufficient, while if it is too large, the compatibility with the binder and the coating strength of the dye layer will decrease,
This is undesirable because it causes problems such as discoloration of the transferred image and storage stability.

Incidentally, the above-mentioned releasable polymer can also be used as a binder in place of the above-mentioned binder.

The thermal transfer sheet of the present invention is prepared by adding necessary additives to the above-mentioned dye, sensitizer, release agent, and binder on at least one side of the above-mentioned base film, which is dissolved in a suitable organic solvent. Alternatively, a dye layer may be formed by coating and drying a dispersion in an organic solvent or water using a forming method such as gravure printing, screen printing, or reverse roll coating using a gravure plate. can get.

The dye layer formed in this way is 0.2 to 5.0+L.
The sublimable dye in the dye layer is preferably 5 to 90% by weight, preferably 10 to 70% by weight of the weight of the dye layer. Preferably, it is present.

When the desired image is a monochrome image, the dye layer to be formed is formed by selecting one color from among the dyes mentioned above, and when the desired image is a full color image, it is formed by selecting an appropriate dye layer such as cyan, magenta, and the like. Select yellow (and black if necessary) to form yellow, magenta, and cyan (further black if necessary) dye layers.

The transfer material used to form an image using the thermal transfer sheet as described above may be any material as long as its recording surface has dye receptivity to the above-mentioned dyes. If the material is paper, metal, glass, synthetic resin, etc. that has no properties, a dye-receiving layer may be formed on at least one surface thereof.

Examples of transfer materials that do not require the formation of a dye-receiving layer include polyolefin resins such as polypropylene, halogenated polymers such as polyvinyl chloride and polyvinylidene chloride, vinyl polymers such as polyvinyl acetate and polyacrylic ester, Polyester resins such as polyethylene terecrate and polybutylene terephthalate, polystyrene resins, polyamide resins, copolymer resins of olefins such as ethylene and propylene and other vinyl monomers,
Examples include fibers, woven fabrics, films, sheets, and molded products made of ionomers, cellulose resins such as cellulose diacetate, and polycarbonates. Particularly preferred are sheets or films made of polyester, or processed paper provided with a polyester layer.

Furthermore, in the present invention, even if the transfer material is non-dyeable such as paper, metal, glass, etc., a solution or dispersion of the dyeable resin as described above is applied to the recording surface and dried. Alternatively, by laminating these resin films, it can be used as a transfer material. Furthermore, even if the transfer material has the dyeability described above, a dye-receiving layer may be formed on the surface thereof from a resin having better dyeability, as in the case of the paper described above.

The dye-receiving layer formed in this manner may be formed from a single material or from a plurality of materials, and may also contain various additives within the range that does not impede the purpose of the present invention. Of course.

Such a dye-receiving layer may have any thickness, but there may be a thickness of 3
The thickness is between 50 μm and 50 μm. Although such a dye-receiving layer is preferably a continuous coating, it may also be formed as a discontinuous coating using a resin emulsion or resin dispersion.

The means for applying thermal energy used when performing thermal transfer using the above-mentioned thermal transfer sheet and the above-mentioned recording material are as follows:
Any conventionally known application means can be used, for example, by controlling the recording time with a recording device such as a thermal printer (for example, Video Printer VY-100 manufactured by Yonichi FF), it is possible to apply an amount of 5 to 100 mJ/m.
A desired image is formed by applying thermal energy of the order of r&.

(Effects) According to the present invention as described below, by making a sensitizer and a specific Bommer mold release agent exist in the dye layer, there is no problem of storage stability or fusion, and it is better than the conventional technology. Images with satisfactory density can be formed with lower printing energy compared to
With the same printing energy as in the past, a thermal transfer sheet is provided that is capable of forming even higher density and finer images.

(Example) Next, the present invention will be described in more detail with reference to reference examples, examples, and comparative examples. In the text, parts or percentages are based on weight unless otherwise specified.

Reference Example 1 Copolymer of 95 mol% methyl methacrylate and 1 to 5 mol% hydroxyethyl methacrylate (molecular weight 120,
000) was dissolved in 400 parts of a mixed solvent of equal amounts of methyl ethyl ketone and toluene, then 10 parts of the above-exemplified polysiloxane compound (5) (molecular weight 3,000) was gradually added dropwise, and the mixture was reacted at 60°C for 5 hours. I let it happen.

The product was homogeneous, and the polysiloxane compound could not be separated by the fractional precipitation method, and it was a reaction between the polysiloxane compound and the acrylic resin. Analysis showed that the amount of polysiloxane segments was approximately 7.4%.

Reference Example 2 50 parts of polyvinyl butyral (degree of polymerization 1,700, hydroxyl group content 33 mol%) was dissolved in 500 parts of a mixed solvent of equal amounts of methyl ethyl ketone and toluene, and then the above-mentioned polysiloxane compound (5) (molecular weight 3, 000)10
of the mixture was gradually added dropwise, and the mixture was reacted at 60° C. for 5 hours.

The product was homogeneous, and the polysiloxane compound could not be separated by the fractional precipitation method, and it was a reaction between the polysiloxane compound and the polyvinyl butyral resin. Analysis showed that the amount of polysiloxane segments was approximately 5.2%.

Reference Example 3 70 parts of a polyester (molecular weight 25,000) consisting of 45 mol% dimethyl terephthalate, 5 mol% monoaminoterephthalic dimethyl ester, and 50 mol% trimethylene glycol were mixed with 700 parts of an equal mixed solvent of methyl ethyl ketone and toluene. and then the exemplified polysiloxane compound (4) (molecular weight to, ooo)
10 parts were gradually added dropwise, and the mixture was reacted at 60° C. for 5 hours.

The product was homogeneous, and the polysiloxane compound could not be separated by the fractional precipitation method, and the polysiloxane compound and the polyester resin were reacted. According to analysis, the amount of polysiloxane segments is approximately 5.4%
Met.

Reference Example 4 80 parts of a polyurethane resin (molecular weight 6,000) obtained from polyethylene adipate diol, butane diol and hexamethylene diisocyanate was dissolved in 800 parts of a mixed solvent of equal amounts of methyl ethyl ketone and toluene, and then the above-mentioned polysiloxane was dissolved. 10 parts of compound (6) (molecular weight 2,000) was gradually added dropwise, and the mixture was reacted at 60° C. for 5 hours.

The product was homogeneous, and the polysiloxane compound could not be separated by the fractional precipitation method, and the polysiloxane compound and the polyurethane resin reacted. According to analysis, the amount of polysiloxane segments is approximately 4.0%
Met.

Reference Example 5 Polysiloxane compound (3) (molecular weight 1.000)
and methacrylic acid chloride in a molar ratio of 1:1, 5 mol% of monomer, methyl meccrylate 45
100 parts of a mixture of 40 mol% of butyl acrylate, 10 mol% of styrene and 3 parts of azobisisobutyronitrile were dissolved in 1.000 parts of a mixed solvent of equal amounts of methyl ethyl ketone and toluene, and the mixture was heated at 70°C for 6 hours. Polymerization was performed to obtain a viscous polymer solution.

The product was homogeneous and the polysiloxane compound could not be separated by fractional precipitation. Analysis showed that the amount of polysiloxane segments was approximately 6.1%.

Reference Example 6 50 parts of styrene-butadiene copolymer (molecular weight 150,000, butadiene 10 mol %) and 2 parts of azobisisobutyronitrile were dissolved in 500 parts of a mixed solvent of equal amounts of methyl ethyl ketone and 1 to 1 to 1 to 1 to 1 to 1 to 1 to 1 to 1 to 1 to 1 to 1 ruene of the same amount of mixed solvent, and then the 10 parts of the illustrated polysiloxane compound (7) (molecular weight 10,000) was gradually added dropwise, and the mixture was reacted at 60° C. for 5 hours.

The product was homogeneous, and the polysiloxane compound could not be separated by the fractional precipitation method, and the polysiloxane compound and the copolymer reacted. Analysis showed that the amount of polysiloxane segments was approximately 6.2%.

Reference Example 7 80 parts of hydroxyethyl cellulose was dissolved in 800 parts of a mixed solvent of equal amounts of methyl ethyl ketone and toluene, and then the above-mentioned polysiloxane compound (6) (molecular weight 2
,000) was gradually added dropwise, and the mixture was reacted at 60'C for 5 hours.

The product was homogeneous, and the polysiloxane compound could not be separated by the fractional precipitation method, and it was a reaction between the polysiloxane compound and hydroxyethyl cellulose. Analysis showed that the amount of polysiloxane segments was about 58%.

Reference Example 8 The above-exemplified fluorocarbon compound (16) was used in place of the polysiloxane compound in Reference Example 1, and the rest were as in Reference Example 1.
A releasable graft copolymer was obtained in the same manner as above.

Reference Example 9 In place of the polysiloxane compound in Reference Example 2, the above-exemplified fluorocarbon compound (Process 8) was used, and the rest were as in Reference Example 2.
A releasable graft copolymer was obtained in the same manner as above.

Reference Example 10 A releasable graft copolymer was obtained in the same manner as in Reference Example 5, except that the methacrylate of the fluorocarbon compound (10) was used in place of the polysiloxane compound in Reference Example 5.

Examples and Comparative Examples The following ink composition for forming a dye layer was applied to the surface of a 6 μm thick polyethylene terephthalate film, which had undergone heat-resistant treatment on the back side of the surface on which the dye layer was to be formed, as a base film to a dry thickness of 1.0 g. Thermal transfer sheets of the present invention and comparative examples in the form of continuous films were prepared by coating and drying by gravure printing so as to give /rrf.

Kayaset Blue 14 (Nippon Kayaku, G, I.

Solvent Blue 63) 5.50 parts Polyvinyl butyral resin (S-LEC BX1)
3.00 parts sensitizer (Table 2 below)
1.00 parts mold release agent (above reference example)
1.00 parts methyl ethyl ketone 22.54
Part 1 Hellen 68. Part 18 Next, synthetic paper (Yubo FPG15 manufactured by Tamago Yuka Co., Ltd.) was used as a base film.
0), a coating solution with the following composition was applied to one side at a rate of 4.5 g/n-f when dry, and the coating solution was heated at 100℃ for 3.
After drying for 0 minutes, transfer materials used in the present invention and comparative examples were obtained.

Polyester resin (manufactured by Toyobo, Vylon200) 11
．． 5 parts vinyl chloride-vinyl acetate copolymer (UCC, VYHH)
5.0 parts amine-modified silicone oil (manufactured by Shin-Etsu Chemical, KF393)
1.2 parts epoxy modified silicone oil (manufactured by Shin-Etsu Chemical, X-22-343)
1.2 parts methyl ethyl ketone 40.8
Part toluene 40.8 parts Cyclohexane 20.4 parts Thermal transfer sheets of the Examples and Comparative Examples and the transfer material are superimposed with the dye layer and image receiving layer facing each other, and the back side of the thermal transfer sheet is From Thermal Head (KMT-85-6,
MPD2), the head applied voltage 12. OV, applied pulse width 16.0 m5ec, /Hne to l m5ec
, a step pattern that sequentially decreases every time, sub-scanning direction 6
Thermal head recording was performed under the conditions of 1 ine/mm (33.3 m5 ec, /]1 ns), and the results shown in Table 2 below were obtained.

(Margins below) Table 2: Relative sensitivity was measured by measuring the printed image density and relatively compared with the printing density of Comparative Example 1 as 1.0. Release property was measured by manually peeling off the thermal transfer sheet after printing. It was determined that

O: Easily peeled off, no problem ×: Difficult to peel off and part of the dye layer was transferred as is.

As described above, according to the present invention, only by adding a specific sensitizer and a release agent to the dye layer, 30
% or more of the concentration improvement effect was obtained, and an excellent mold release effect was obtained.

Claims (7)

[Claims] (1) In a thermal transfer sheet in which a dye layer consisting of a dye, a binder, a sensitizer, and a release agent is provided on a base film,
The sensitizer is a low molecular weight substance with a melting point of 50 to 150°C, and the release agent is at least one selected from polysiloxane segments, fluorocarbon segments, and long-chain alkyl segments grafted onto the main chain. A thermal transfer sheet characterized by being a graft copolymer having releasable segments. (2) The thermal transfer sheet according to claim 1, wherein the main chain of the releasable polymer is compatible with the binder. (3) The thermal transfer sheet according to claim 1, wherein the main chain of the releasable polymer is an acrylic, vinyl, polyester, polyurethane, polyamide, or cellulose resin. (4) The thermal transfer sheet according to claim 1, wherein the low molecular weight substance has a molecular weight of 100 to 1,500. (5) The thermal transfer sheet according to claim 1, wherein the amount of the low molecular weight substance is 1 to 100 parts by weight per 100 parts by weight of the binder. (6) The thermal transfer sheet according to claim 1, wherein the binder has a Tg of 50°C or higher. (7) The thermal transfer sheet according to claim 1, wherein the surface of the base sheet is treated to facilitate adhesion.